Detection of the Electric Potential Surface Distribution with a Local Probe Based on a Field Effect Transistor with a Nanowire Channel

A non-destructive method of scanning probe microscopy for simultaneous measurements of the surface topography and electric field (charge, potential) distribution is demonstrated. The surface is scanned by the tuning fork method, the interaction with the surface is carried out by the sharp edge of the silicon chip mounted on one of the prong of the quartz resonator. The detection of electric potentials was performed using a field-effect transistor with a nanowire channel formed at the apex of the probe. Due to the low Q factor of the oscillatory system, scanning with standard algorithms of probe movement leads to fast wearing and even destruction of the apex of the probe. An original scanning algorithm was developed that minimizes the interaction time between the probe and the object under study. The minimal time at each scanning surface point is 1.0–1.6 ms and is determined response time of the field-effect transistor to a change in the detected electric field (the measuring time per frame is 20–30 min). The spatial resolution of the method is 10 nm for topography and 20 nm for the sample field profile. The field resolution of our chips is in the range of 2–5 mV and is determined by the sensitivity of the nanowire of the field effect transistor and the distance from the nanowire to the probe apex.